The Apple iPhone 4S, left, is displayed next to the Samsung Galaxy S III at a store in San Francisco. / Marcio Jose Sanchez, AP

by Rob Pegoraro, Special for USA TODAY

by Rob Pegoraro, Special for USA TODAY

Question: Will 8 gigabytes leave me with enough storage space on a smartphone?

Answer. Look on your own computer first: The volume of songs, photos and (especially) videos that you'd want to copy to the phone from there will provide your answer.

Apps by themselves generally don't take up much space. Most of them run less than 50 megabytes. For instance, Facebook is a 41-megabyte download on an iPhone and 17 MB on my Android phone. Only a thimbleful of apps, such as Apple's 496 MB iMovie and action games like Asphalt 8: Airborne, 884 MB on an iPhone, and Grand Theft Auto III, 1.2 GB on an Android phone, make a meaningful dent in your device's capacity.

Audio and image files don't take up much space on their own (unless you're taking photos with the Nokia 1020's 41-megapixel camera), and even in bulk it's hard to fill up a phone with those alone. Any one movie, however, can gobble up hundreds of megs by itself.

Fortunately, you don't need to keep your entire music, picture and video library on your phone - as long as you can sync over enough to keep yourself entertained on a long flight or on vacation, you should be fine. You can also supplement whatever's on your phone with content streamed from apps like Spotify, Pandora or Netflix (though live video can eat into a bandwidth cap).

With all that in mind, I think most non-intensive users who aren't looking to watch movies on the screen in their pocket will be fine buying the smallest capacity available. That's usually 8 GB, but Apple's iPhone 5, Samsung's Galaxy S 4 and other high-profile devices start at 16 GB.

If you plan to keep a few flicks on your phone or can't live without having a large fraction of your music collection available, buy the next step up, 16 or 32 GB - unless the model you have in mind lets you add storage with a microSD card. Those are laughably cheap, with 32 GB cards going for $20 and change.

Remember that you won't get the full capacity advertised, since system files and bundled apps eat up some of the storage. (You also lose a bit because vendors artificially define a gigabyte as 1 billion bytes when it's actually 1,073,741,824 bytes.)

But that gap varies by operating system and manufacturer. On 16 GB iPhones, users report having from 13 to 14 gigs available, and an 8 GB Nexus 4 gives the user 5.7 GB to play with. But on a freshly-reset Galaxy S 4, I saw only 9.1 GB at the user's disposal (that's why there's no 8GB model), and HTC's 8 GB 8XT Windows Phone had just 4.8 GB available out of the box.

Most users will still be fine with those limited allocations, but phone vendors and wireless carriers ought to disclose them upfront.

Tip: With Android Device Manager, Google finally helps you find a lost phone

Android users no longer need to install extra programs to locate a missing phone, force it to ring and, if necessary, erase it remotely: In early August, Google launched a free Android Device Manager service. To activate it, sign into the ADM page with your Google account and follow its prompts to change the settings on your phone that will grant the service permission to find and wipe your phone.

I tested this a couple of weeks ago on a loaner phone and can confirm it works as advertised. But without the ability to push a message to a lost phone's screen ("Return this by 5 p.m. or the drone strikes commence"), Android Device Manager doesn't match the utility of third-party options like Lookout and Android Lost - or the find-my-phone tools that Apple and Microsoft have shipped with iOS and Windows Phone since 2010.